Energy recovery ventilator with self-contained dehumidification system

ABSTRACT

An air conditioning system that includes an energy recovery ventilator that transfers energy between a supply air stream and an exhaust air stream. Downstream of the energy recovery ventilator are multiple refrigeration circuits that reject heat into both the supply air stream and the exhaust air stream. The use of the multiple refrigeration circuits eliminates the need to mount outdoor equipment and provide piping for a cooling system.

BACKGROUND OF THE INVENTION

This invention is directed to a dehumidification system and more particularly to an outdoor air dehumidification system that utilizes an energy recovery ventilator that reduces the amount of cooling needed, and then utilizes both supply and return air streams to reject the heat from the refrigeration system as it dehumidifies the outdoor air brought into a building.

Air conditioning systems are known in the art and typically bring outdoor air indoors to maintain the health of indoor spaces. This presents challenges as, particularly in certain parts of the country, the outdoor air contains humidity levels that are unsafe when brought indoors and lead to mold growth and occupant discomfort.

Presently, there are two ways of confronting this problem. First, the outdoor air is brought into a main air conditioning system where the outdoor air is cooled along with the main cooling stream to remove excess humidity (i.e. 55° F.). While useful, this process often results in overcooling or a need to reheat the air as the cooling system runs continuously to remove the excess humidity.

A second way brings the outdoor air in through a dedicated outdoor air system (DOAS) where the outdoor air is delivered to an interior space through ductwork. Often, the DOAS will use an energy recovery ventilator (ERV) to reduce energy consumption associated with heating and cooling air during different seasons. The DOAS can be adapted to have heating and cooling systems to neutralize air to the space, provide both dehumidification and heating based on the season. The main heating and cooling system can then be downsized and simplified to satisfy only space loads (outdoor air loads being handled by the DOAS).

Basically, there are four common DOAS arrangements and one less so common. In a first example, the DOAS has an ERV with no cooling system that combines air leaving and entering a building in a heat exchanger to transfer 50% to 75% of the energy between the two air streams. For example, if the fresh outdoor stream of air is 0° F., and the stale/polluted exhaust being removed from the building were 70° F., the heat exchanger of the ERV would heat the outdoor stream to 50° F. by removing heat from the exhaust stream, resulting in the exhaust stream being cooled to 20° F. The problem with this system is a large amount of heating or cooling load is left and must be handled by the indoor units.

In a second example, the ERV is combined with air cooled direct expansion (DX) refrigeration units. The DX refrigeration units take the heat from the cooling and dehumidifying system and reject the heat into the atmosphere at the DX refrigeration unit through an air cooled condenser. The problem with this DOAS arrangement is that it can only be mounted outside the building.

A third example uses air cooled split DX systems combined with an indoor handler or ERV, and a remote outdoor condenser that rejects heat into the atmosphere. The disadvantage of this arrangement is that additional piping is needed that increases installation costs.

A fourth DOAS arrangement utilizes a chilled water system where cold water is used at the air handler. The disadvantage of this arrangement is that it requires piping and chiller installation, which significantly increases cost.

Finally, a fifth less common DOAS arrangement is to use a DX refrigerant cooling coil that uses a supply air stream condenser to reject all of the heat from the refrigeration circuit. In this arrangement, the DX refrigerant cooling coil cools the outdoor air stream after it leaves the ERV and then rejects all of the energy from the refrigeration circuit back into the air stream entering the building. The problem with this system is that the supply air stream temperature is very warm (typically above 100° F.) as it enters the building. Accordingly, a need exists in the art for a system that addresses these problems, disadvantages, and deficiencies.

An objective of the present invention is to provide an air conditioning system that eliminates the need for mounting outdoor components.

Another objective of the present invention is to provide an air conditioning system that eliminates the need to provide piping for a cooling system.

A still further objective of the present invention is to provide an air conditioning system that more efficiently utilizes an energy recovery ventilator.

These and other objectives will become apparent to those skilled in the art based upon the following written description, drawings, and claims.

SUMMARY OF THE INVENTION

An air conditioning system having an energy recovery ventilator that includes a plate heat exchanger or heat wheel or other type of air-to-air heat exchanger. A supply air stream flows from an outside air intake through the heat exchanger to a supply fan that distributes conditioned fresh air into a building. An exhaust air stream flows from within the building through the heat exchanger to an exhaust fan where the exhaust air stream is discharged outside the building. Within the heat exchanger the supply air stream and the exhaust air stream cross and transfer energy.

Downstream of the heat exchanger are multiple refrigeration circuits that dehumidify the outdoor air stream and reject heat into both the supply air stream and the exhaust air stream. In the supply air stream there is a DX coil and one condenser coil. In the exhaust air stream is an additional condenser coil. The compressors can be located anywhere within the unit or very near the unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an energy recovery ventilator; and

FIG. 2 is a schematic view of an energy recovery ventilator.

DETAILED DESCRIPTION

Referring to the Figures the air conditioning system 10 includes an energy recovery ventilator (ERV) 12. The ERV is of any type such as a heat wheel, heat plate exchanger, air-to-air, or other type of heat recovery device. The system 10 includes a supply air stream 14 that flows from an outside air intake through a filter 16 to the ERV heat exchanger 12 to a supply fan 18. Alternatively, the supply fan is positioned anywhere along the supply air stream.

The system 10 also has an exhaust air stream 20 that flows from indoors through a second filter 22 to the ERV heat exchanger 12 to an exhaust fan 24. The exhaust fan 24 can be located anywhere along the exhaust air stream. Within the ERV heat exchanger 12 in one example the supply air stream 14 and the exhaust air stream 20 cross and energy is transferred between the two air streams.

Downstream of the heat exchanger 12 are multiple refrigeration circuits 26 that are positioned to divide the cooling/dehumidification load and reject heat into the air streams 14 and 20. Preferably, the multiple refrigeration circuits 26 have all components contained in a packaged system. By providing the refrigeration circuits in this manner, the need to mount outdoor equipment or provide piping for the cooling system is eliminated.

In the example shown, the supply air stream 14 flows through a cooling coil 28 downstream of the heat exchanger 12 and then flows through a condensing coil 30 to the supply fan 18 and then into the building. The exhaust air stream 20 flows from the heat exchanger 12 to a first 32 then a second compressor 34 (the exact location of the compressors is not critical to unit function). From the second compressor 34 the exhaust air stream 20 flows through a second condensing coil 36 to the exhaust fan 24 and then exhausted outside the building. The effect of the system on the air streams, by example only, is that upon exiting the heat exchanger 12 the supply air stream 14 has a temperature of about 80° F. Upon exiting the cooling coil 28 the supply air stream 14 is cooled to 55° F. thus removing surplus/undesirable humidity. Finally upon exiting the condensing coil 30 the supply air stream 14 is heated to 85° F.

At the same time, the exhaust air stream 20 enters the heat exchanger 12 at 75° F. and exits the heat exchanger 12 at 89° F. After passing through the first 32 and second 34 compressors and the second condensing coil 36 the exhaust air stream is heated to 120° F. In essence, the cooling coil 28 uses multiple refrigeration circuits to reject heat into the supply air stream 14 after the cooling coil 28 and into the exhaust air stream 20 after the heat exchanger 12.

Additional accessories may be added to the system as desired. For example, a heating coil 38 could be added to the system anywhere after the heat exchanger 12 in the supply air stream for winter heating and the refrigeration circuit could be reversible for winter heating. Also, a bypass damper 40 could be added between the return (from space) to the supply (to space) to permit recirculation of air for unoccupied mode dehumidification during humid weather. In this mode only the cooling circuit/circuits that rejected heat into the supply air stream would run.

A bypass damper 40 could also be added between the outdoor air path to the exhaust air path to allow some outdoor air to go directly to the second condensing coil 36 to reduce exhaust air from the building. Finally, the compressors 32 and 34 could be modulating.

Accordingly, an air conditioning system has been disclosed that at the very least meets all the stated objectives.

From the above discussion and accompanying figures and claims it will be appreciated that the air conditioning system 10 offers many advantages over the prior art. It will be appreciated further by those skilled in the art that other various modifications could be made to the device without parting from the spirit and scope of this invention. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby. It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in the light thereof will be suggested to persons skilled in the art and are to be included in the spirit and purview of this application. 

What is claimed is:
 1. An air conditioning system, comprising: an energy recovery ventilator; a supply air stream and an exhaust air stream that flow through the energy recovery ventilator; and multiple refrigeration circuits positioned to divide a cooling load and reject heat into both the supply air stream and the exhaust air stream.
 2. The system of claim 1 wherein the energy recovery ventilator includes an air-to-air heat exchanger.
 3. The system of claim 1 wherein the multiple refrigeration circuits include a cooling coil and a condensing coil positioned along the supply air stream.
 4. The system of claim 1 wherein the multiple refrigeration circuits with all components are contained in a packaged system.
 5. The system of claim 1 wherein the multiple refrigeration circuits include a cooling coil along the supply air stream that rejects heat into the supply air stream after the cooling coil and into the exhaust air stream after a heat exchanger of the energy recovery ventilator. 